Optical fiber detectors afford many specific advantages: limited space requirement, reduced mass, large passband and low attenuation, immunity to electromagnetic interferences, good resistance to the effects of ionizing radiations, possibility of multiplexed reading of the signals produced by various detectors and considerable measuring point offset, etc.
The prior art in this sphere can be illustrated notably by the following patents: U.S. Pat. No. 4,932,262; U.S. Pat. No. 5,317,929; U.S. Pat. No. 5,600,070; WO-99/13,307 (U.S. Pat. No. 6,016,702); WO-00/00,799; WO-01/14,843 or EP-1,008,840 A1.
The pressure detectors comprise for example one or more deformable elements (diaphragm, bellows, etc.) one surface of which is subjected to the pressure prevailing in a medium, the other surface being subjected to a reference pressure. The deformations or displacements of these elements under the effect of the pressure variations in the medium are translated into variations in the length of an optical fiber portion with Bragg gratings that connects the mobile element to a fixed housing. A detector of the same type is often associated with these pressure detectors, on an optical fiber portion that is not subjected to a stress where the grating deformations are only due to temperature variations. Standard type Bragg gratings can for example be used, whose mean spectral width is of the order of 200 pm or, for higher precision, phase jump type Bragg gratings whose spectral width is reduced to some picometers (pm), as described for example in patent application WO-9,959,009.